What does the preservation of facial nerve CMAPs indicate?

The preservation of facial nerve compound muscle action potentials (CMAPs) during surgery serves as an important neurophysiological indicator. When facial nerve CMAPs are preserved, it suggests that the nerve is intact and conduction is occurring. However, this finding does not guarantee that the facial nerve will function normally postoperatively or that there won't be other complications.

CMAPs can sometimes be preserved even in cases where the nerve has been manipulated or at risk, and immediate postoperative assessments may reveal varying degrees of facial dysfunction. Therefore, while intact CMAPs are a positive sign during surgery, they do not always correlate with a favorable surgical outcome or complete preservation of motor function.

Understanding this nuance is critical for neurophysiologists and surgeons. They must recognize that factors such as the degree of trauma during surgery, the timing of assessments, and individual patient anatomy can affect the ultimate outcome. Hence, the correct interpretation of preserved CMAPs is that while they suggest some level of nerve integrity, they do not always lead to a good surgical outcome.